1. Field of the Invention
The present invention relates generally to an energy efficient robotic system, and more specifically, to an energy efficient robotic system with passive-dynamic locomotion.
2. Description of the Related Art
Various types of robotic systems are known that mimic human functions, such as locomotion, talking, manipulating an object or the like. Human walking is a complex function involving the coordinated activity of the foot, ankle, leg and hip, as well as the arms and brain. One example of a robotic system that has the ability to walk and a human-like form is a bipedal robot. The bipedal robot requires precise actuators and sophisticated control strategies, in order to mimic human walking by actively controlling every joint angle in the leg and foot, so that the center of mass of the robot remains as level as possible. However, this type of controlled gait is much less efficient than an actual human walking gait. As a result, the bipedal robot requires greater energy expenditure, as compared to that of a walking comparably sized human.
More recently, it has been demonstrated that walking with a less smooth gait, where the center of mass rises and falls in an oscillatory manner with each step, provides a significant increase in movement efficiency, thereby reducing the energy output level to one more comparable with human walking. An example of a robotic system with an oscillatory gait is a passive-dynamic walker. The passive-dynamic walker is a simple machine that models the leg position of the robot as a passive mechanical structure, and utilizes the dynamic motion of the robot's swinging limbs to propel the machine. The early passive-dynamic walkers relied on the force of gravity to walk down an inclined surface. More recently, passive-dynamic walkers have been developed which utilize at least one active power source that enables the machine to walk on level ground. The gait of the passive-dynamic walker is remarkably humanlike, and resembles an up/down motion of the center of mass as the foot strikes the surface and then pushes upward off the surface. Since the passive-dynamic walker does not rely primarily on constantly energized controllers and actuators to control joint angles, it uses less energy than a comparable bipedal robot.
The control capabilities of robotic systems have increased in recent years. However, the energy storage capability of most robotic systems remains a fundamental limitation. Although the previously described passive-dynamic walker requires less energy than a dynamic robotic system, the passive-dynamic walker robotic system is still limited by the power requirements. Thus, there is the need in the art for a passive-dynamic robotic system that incorporates a renewable energy source in order to increase the efficiency of the energy usage of the robotic system.